1. Field of the Invention
The present invention relates to a gas-insulated equipment, and more particularly to a gas-insulated equipment such as a gas-insulated switchgear which is miniaturized through improvement in its insulation capability.
2. Background Art
A conventional gas-insulated switchgear has a connection between high-voltage conductors, and shielding electrodes having a larger diameter than that of the high-voltage conductors are provided at the connection to reduce electric field thereat. The maximum electric field is generated at the shielding electrodes, and the ratio of the maximum electric field intensity to the electric field intensity at the high-voltage conductors is generally about 1.25:1. For miniaturizing the gas-insulated switchgear, dielectric strength in the vicinity of the area at which the maximum electric field is generated needs to be increased, and a method of improving dielectric strength by covering the metal electrode surface in this area with thick dielectric coating has been disclosed (for example, see JP-A-2004-222483, pp. 3-6, FIGS. 7 and 11).
According to the above related-art method, the dielectric strength of the thick dielectric coating is approximately 1.45 times larger than that of a bare electrode. However, since the ratio of the maximum electric field intensity of the shielding electrode to the electric field intensity of the high-voltage conductor is about 1.25:1 as mentioned above, the dielectric strength of the bare electrode high-voltage conductor is insufficient. Thus, improvement in the dielectric strength of the entire electrode system needed for miniaturization of the device cannot be attained.